Thread rolling machine



April 19, 1960 AKIRA YAMAMOTO 2,932,996

THREAD ROLLING MACHINE Filed Dec. 2, 1955 4 Sheets-Sheet l INVENTOR Z4K/RA YAMA April 1960 AKIRA YAMAMOTQ 2,932,996

THREAD ROLLING MACHINE Filed Dec. 2, 1955 4 Sheets-Sheet 2 2?. 4-INVENTOR Ala/2A yam/ 2670 April 19, 1960 AKIRA YAMAMOTO THREAD ROLLINGMACHINE 4 Sheets-Sheet 4 Filed Dec. 2, 1955 INVENTOR.

AK/RA VAMAMOTO BY MW United States Patent THREAD ROLLING MACHINE AkiraYamamoto, Shibuya-ku, Tokyo, Japan, assignor to Akashi Seisakusho, Ltd.,Tokyo, Japan, a corporation of Japan Application December 2, 1955,Serial No. 550,666

3 Claims. (Cl. 80-6) This invention relates in general to a continuouslyoperating, fully automatic machine for cold rolling threads into aplurality of screw blanksand, more particularly, to a type thereofwherein the threads are produced upon said blanks by advancing thembetween the spaced peripheries of a pair of radially aligned,cylindrical dies.

This application is a continuation-in-part of my application Serial No.509,957, filed May 20, 1955, and entitled Continuous Thread Cold RollingProcess and Machine, now abandoned. As stated in said co-pendingapplication Serial No. 509,957, several machines and methods have beendeveloped for cold rolling threads, particularly on screw blanks.However, insofar as I am aware, the present thread rolling machineswhich have a high output capacity produce inferior threads, and thosepresent machines, which produce high quality, rolled threads, have arelatively low output capacity. Thus, insofar as I am aware, a coldthread rolling machine capable of continuously producing largequantities of high quality screw threads at a rapid output rate has notbeen produced prior to my invention disclosed herein.

Attempts have been made in the past to produce such a machine, asdemonstrated by the Landis Patent No. 1,107,621, issued in 1914.However, although the Landis patent expired more than twenty years ago,the machine represented by the Landis patent has never, so far as Iknow, received commercial acceptance. It is my belief that this non-useis due to the inability of previous machine like the Landis machine toproduce high quality screw threads at a rapid rate.

Accordingly, a primary object of this invention is the provision of arelatively small, compact machine of great strength and durability, forautomatically and continuously producing high quality screw threads upona plurality of successively fed blanks at a relatively high rate ofoutput, said machine being of the type having a pair of radiallyaligned, cylindrical die rollers peripherally spaced from each other androtatable in the same direc tion upon substantially parallel axes.

A further object of this invention is the provision of a machine, asaforesaid, wherein the die rollers have different peripheral speeds,wherein guide mechanism is provided for conveying screw blanks to apoint between the die rolls and said guide mechanism moves between saidrolls at speed substantially equal to one-half the difference in saidperipheral speeds, and wherein means is provided whereby the screwblanks will move and be advanced between said rolls slightly faster thansaid speed of said guide mechanism, thereby preventing injury to theexpanding diameter of the screw blank as the thread is being rolledthereinto.

A further object of this invention is the provision of a thread rollingmachine, as aforesaid, having adjustment means for momentarilyincreasing or decreasing the speed of movement of said guide mechanismbetween said die rolls for the purpose of adjusting and controlling the2,932,996 v Patented Apr. 19, 1960 phase or peripheral relationship ofsaid dlie rollers with respect to the screw blanks being threadedthereby.

A further object of this invention is the provision of a thread rollingmachine, as aforesaid, whereby threads of various pitches and pitchdiameters may be produced by changing the die rollers and the distancebetween the axes thereof, but, however, wherein the distance betweensaid rollers, once established for any given screw thread, is maintainedsubstantially constant, within close tolerances, throughout the entirecontinuous operation of a machine, thereby eliminating the need for anytype of device for reciprocating one of said rollers with respect to theother during any part of the thread rolling operation.

Other objects and purposes of this invention will become apparent topersons familiar with this type of machine upon reading the followingspecification and examining the accompanying drawings, in which:

Figure 1 is a top plan view of said thread rolling machine, embodying myinvention.

Figure 2 is the side elevation view of said machine, ineluding a supportbase therefor.

Figure 3 is a sectional view, taken along the line III- III of Figure 1.

Figure 4 is a sectional view, taken along the line IV--IV of Figure 1.

Figure 5 is a sectional view, taken along the line V-V of Figure 2.

Figure 6 is a sectional view, taken along the line VI- VI of Figure 3.

Figure 7 is a sectional view, taken along the line of VI I-VII of Figure3.

Figure 8 is a sectional view, substantially as taken along the lineVHI-VIII of Figure 1.

Figure 9 is a sectional view, taken along the line IX- IX of Figure 4.

Figure 10 is a sectional view, taken along the line X-X of Figure 9.

Figure 11 is an overlay of opposing portions of the peripheries of apair of die rolls, with said peripheries distorted into planarpositions.

Figure 12 is a side elevation view of a portion of a threaded screw withthe screw blank from which it was rolled shown in broken lines.

Figure 13 is an overlay of the corresponding portions of the peripheriesof said die rolls engaged by the screw shown in Figure 12 during arotation thereof.

For the purpose of convenience in description, the terms front, rear,and derivatives thereof, will have reference to the leftward andrightward ends of the machine as appearing in Figure 1. The terms upper,lower, and derivatives thereof, will have reference to the machine asappearing in Figure 2. The terms lef right," and derivatives thereof,will have reference to the machine as appearing in Figure 4. The termsinner, outer, and derivatives thereof, will have reference to thegeometric center of said machine and parts thereof.

General description In order to meet the objects and purposes set forthabove, as well as others related thereto, I have provided an automaticmachine 10 (Figures 1 and 2) for cold rolling threads into a pluralityof cylindrical blanks continuously fed to, and advanced between, thespaced, radially aligned peripheries of a pair of cylindrical die rolls11 and 12 forming a part of said machine. The die rolls 1i and 12, whichare rotated in the same direction, are supported by the housings 13 and14, which are in turn mounted upon the machine base 15. A cylindricalfeed shell 16, which concentrically surrounds one of said die rolls, isprovided with a plurality of slots 17 thereaeeasee 3 through forreceiving said cylindrical blanks and feeding them between said dierollsat a preselected speed which varies with the difference between theperipheral speeds of said die rolls 11 and 12.

Detailed construction As shown in Figures 1 and 4, the housings 13 and14 of the thread rolling machine 11 contain'substantially parallel, diesupporting shafts 21 and 22, respectively. in this particularembodiment, the housing 13 is releasably secured to the base 15 bymeans, such as the bolts 13. When the bolts 18 areloosened, housing 13ispivotablc with respect to said base about the pivot pin 20 for thepurpose of adjusting the axis of the shaft 21 With respect to the axisof the shaft 22. The housing 14 is releasably secured upon the base 15by means of the transverse guide rails 23 and 24 and the clampingmembers 25 and 26 and adjustably movable toward and away from thehousing 13. A pair of parallel, transverse tie rods 27 and 28 aresecured upon, and extend through, the housings 13 and 14 above andbelow, respectively, the shafts 21 and 22. Said tie rods 27 and 28 arethreaded at their opposite ends and engaged by internally threadedlocking collars 29 for positioning and holding the housing 14 withrespect to the housing 13 in a substantially conventional manner.

The rear ends of the housings 13 and 14 are provided with gear boxes 31and 32 for connecting the die shafts 21 and 22, respectively, to atransverse power shaft 33 in a conventional manner, said power shaftbeing driven by any convenient means, not shown. Thus, by appropriateselection of gear ratios in the gear boxes 31 and 32, said die shafts 21and 22 may be rotated at the same or different rotational speeds, asdesired or required. In this particular embodiment, said shafts 21 and22 rotate at different rotational speeds.

The die rolls 11 and 12 are mounted upon, and rotatable with, the dieshafts 21 and 22, respectively, near the frontward ends thereof andforwardly of the housings 13 and 14. A pair of coupling heads 34 and 35are rotatably supported upon the extreme front ends of said die shafts21 and 22, respectively, and are adjustably connected to each other by apair of parallel connecting rods 36 and 37, which are substantiallyparallel with the tie rods 27 and 28. As will be seen hereinafter, theheads 34 and 35 and the rods 27, 28, 36 and 37 oppose lateral movementof the die shafts 21 and 22 away from each other during the threadrolling operation, that is, when a blank is' passing between the dierolls 11 and 12.

An external gear 40 (Figure 3) is mounted upon, and rotatable with, thedie shaft 22, adjacent to the rearward face of the die roller 12. Aplanet carrier, 38, which encircles the gear 40, rotatably supports aplurality of planet gears 39 uniformly spaced around the perimeter ofsaid gear 40. Said planet gears 39 are simultaneously engaged by theinternal teeth 41 and 42 of a pair of adjacent internal gears 43 and 44,respectively. The rear ring gear 44 also has external teeth 45, whichare engageable with a worm 46 (Figure 4) rotatably mounted upon thehousing 14 with its axis in a vertical position. The worm 46 is securedupon a vertical shaft 47 having an adjusting head 48 at the upper endthereof.

The front ring gear 43 is secured to, and rotatable with, the feed shell16. The feed shell 16 is provided with a plurality of elongated slots17, which are preferably parallel with each other and with the axis of.the die shaft 22. Said slots 17 are disposed uniformly along theperiphery of the feed shell 16 and preferably extend completely acrossthat portion of the shell which passes between the die rolls 11 and .12.Said feed shell '16 is of such thickness that it will pass between saiddie rolls 11 and 12 without interference of any kind therewith. Means,such as the chute 30, is provided for feeding screw blanks 50 from asource, not shown, into the slots 17 in the feed shell 16. v 7

As shown in Figure'7, the internal teeth 41- on the'front 4 ring gear 43have a different pitch than the internal teeth 42 on the rear ring gear44, even through both ring gears engage the same planet gears 39simultaneously. The rear ring gear 44 is normally held in fixed positionby its engagement with the worm 46. Thus, rotation of the external gear40 rotates the planet gears 39 within said ring gears 43 and 44 andthereby effects a circumferential advancement, herein referred to as aprofile shift, of the front ring gear 43 with respect to the rear ringgear 44.

The said profile shift of the front ring gear 43 may be varied byvarying the difference between the pitches of the two sets of internalteeth 41 and 42. This profile shift of the front ring gear 43 isselected so that the feed shell 16 will have a peripheral speedapproximately equal to one-half the difference between the peripheralspeeds of the die rolls '11 and 12.

Ordinarily, the feed shell 16 will encircle that die roll, here theright roll 12, whose periphery moves downwardly between the two rolls.In this case, die roll 12 will normally be the faster moving roll, sothat said shell will be moving downwardly between said die rolls and thefeeding operation will not be opposed bygravity. However, this is amatter of choice and feeding could be directed upwardly, if desired.Also, the shell 16 may encircle the slower moving die, here the die 11,and, by proper selection of the teeth 41 and 42, the.

shell 16 may be caused torotate counter to thedie 11 and produce thesame downward feeding. In any event, the direction of movement of theshell 16 between the die rollswill always be the same as the directionof movement of the faster moving one of said peripheries between saidrolls.

The peripheries of the die rolls 11 and 12 are each provided with .aplurality of helical grooves 51 (Figures 9,

10, 11 and 13), having thesame pitch and depth as the thread which theywill produce upon the cylindrical blank 50 passing thercbetween. Theslope of said helical grooves 51 with respect to a plane 49 (Figure 11)passing perpendicularly through the axes of the die rolls 11 and 12will, in this particular embodiment, be identical on both die rolls,even though said rolls will have different peripheral speeds. Thus, asshown in Figures ll and 13, the helical grooves 51 on one die roll (insolid lines) will intersect the grooves on the other die roll (in brokenlines) when. superimposed upon each other, at points defining parallellines a, which are substantially parallel with the axes of said rolls.It will be observed that there will be two lines a of intersectingpoints for each start b of a helical groove 51 along one edge of a dieroll, The number of starts b on a particular die roll, hence the slopeof said helical grooves 51, will depend upon the pitch of the thread 52(Figure 12) being produced upon the screw 53. The distance between anytwo adjacent lines a is equal to one-half the circumference of the screwblank 50 being threaded. Thus, since the peripheries of said die rollsmove past each other in opposing directions, the movement by each dieperiphery of said distance between adjacent lines a will rotate saidblank degrees.

On .a conventional screw, as indicated in Figure 12,3 thread root 54 isdiametrically opposite to a thread ridge 55 at all times along the axisX of the screw 53. Accordingly, when the axis X (Figure 10) of the screwblank 50 passes through the plane'Y (Figures 10 and 13), defined by theaxes of the die rolls 11 and 12, the roots on one die ,roll'will beoppositethe ridges on the other 'die roll. This arrangement of rootsopposite ridgeswill be referred to hereinafter as being in phase.

For the screw blank 50 to be moved or fed in a direction transverse toits axis, as downwardly, for example, the said; phase between the rootsand ridges on the die rollperipher'ies must move downwardly also, andthis is accomplished by, providing a faster peripheral speed on that onepf said dies whose periphery moves down-' Wardly between the'dies, heredie'roll 12.

As shown in Figure 13 by plane Y, the proper phase occurs midway betweeneach pair of adjacent lines a. Thus, the number of slots 17 in the shell16 is limited to the number of lines a, or twice the number of starts b,on the die roll which it encircles. The distance between said slots is,therefore, necessarily equal to the distance between a pair of adjacentlines a or an even multiple thereof. The feed shell 16 must besynchronized so that it has a slot 17 passing through said plane Y eachtime a phase passes through said plane Y. Due to the rolling movement ofthe screw blank 50 between the die rolls, the speed of said phasepassage is equal to one-half the difference of the peripheral speeds ofsaid dies.

Referring to Figure 10, it will be observed that the screw blank 50 hasan outside diameter which is some what smaller than the outside diameterof the finished screw 53 after the thread rolling process is complete.Thus, if the trailing wall 58 of a slot 17 is snugly against theperiphery of the blank 50 as it enters between the die rolls 11 and 12,the way it should be, then some means must be provided for acceleratingthe screw 53 to provide room for the expansion of its outside diameterduring the rolling process. This expansion is represented by thedistance between the center lines X and X (Figure of the finished screw53 and the original blank 50, respectively. As shown in Figure 13, suchexpansion urges the screw axis X to pass through the plane Y in advanceof said phase, which tends either to score the trailing wall 58 of theslot 17 or to jam the threads 52 on the screw 53.

Having recognized the problem and its cause, I have conceived severalmethods of accelerating the movement of said screw blank Strand/or saidphase with respect to the movement of the slot 17, as said blank 50 isengaged between the opposing surfaces of the die rolls 11 and 12, andthereby overcoming the problem. One such method is produced by slightlyincreasing, as by 1%, the diameter of the faster moving of the two rollswithout changing any other aspect in the relationships between the shell16 and the two rolls. This will cause the phase, hence the center line Xof the screw 53, to move slightly faster than the slot 17 as it passesbetween the two die rolls. Here it is assumed that the die rolls hadidentical diameters before such increase in one diameter, and that theyobtain their different peripheral speeds by being rotated at differentangular speeds.

Another method of overcoming this problem, as shown in Figure 8, is tomount one of the die rolls, such as the die roll 11, so that it isaxially slidable on its shaft 21. Resilient means, such as the springs59, are provided upon both sides of said roll whereby the roll may bedeflected axially a slight amount. Thus, when the increase in diameterof the screw blank 50 causes the blank to move ahead of the phase, theresiliently mounted roll shifts axially, which temporarily advances thephase and thereby prevents damage to the thread being produced on thescrew.

Where the die rolls have the same rotational speed and the difference intheir peripheral speeds is produced by having different diameters,approximately the same means may be used to prevent the injuries to thescrew threads due to the expansion in the screw blank 51) during therolling process. It will be recognized that, in order to maintain thesame pitch and slope of the helical grooves on die rolls havingdifferent diameters, more starts b will be required on the largerdiameter roll than on the smaller diameter roll. However, as in the caseof the die rolls having the same diameters, the acceleration of thescrew is accomplished without changing the number of starts. Suchacceleration is effected by slightly reducing the ratio between thediameters of said rolls, or by using the springs 59, shown in Figure 8,and no other alteration is required.

Means, such as the guide strips 61 and 62 (Figures 1.

6 2 and 4), may be resiliently mounted upon a rod 63 parallel with thedie shaft 22 for holding the screw blanks 50 within the slot 17 (Figure9) as they approach a position between the die rolls 11 and 12. A spacercollar 64 encircles the die shaft 22 between the feed shell 16 and thecoupling head 35. Oil, or any other convenient combination coolant andlubricant, may be supplied through means such as the pipe 65 to a pointabove the space between the die rolls 11 and 12 for feeding suchlubricant onto the screw blanks as they are rolled between the die rolls11 and 12.

Operation As indicated generally in the above description, the machine10 is prepared for operation by placing the proper sized die rolls 11and 12 upon their respective die shafts 21 and 22, and by properadjustment of the die rolls 11 and 12 with respect to each other. Suchadjustment is effected by means of the guide rails 23 and 24, theclamping members 25 and 26, the locking collars 29, on the guide rods 27and 28, and the connect ing rods 36 and 37. It has been found that, insome instances, the tolerances in the bearings supporting the die shafts21 and 22 may permit a deflection of one of the die shafts 21 and 22with respect to the other to the extent of such tolerance during therolling of the threads 52 upon the blanks 50. The result of thisdeflection is to place the die shafts 21 and 22 slightly out of aparallel attitude with respect to each other. In order to overcome thisproblem, the housing 13 is pivoted around the pivot pin 20 so that itsshaft 21 is slightly out of parallel with the shaft 22 in housing 14,and both housings are then secured to the base 15. Thus, when the blanks50 pass between the die rolls 11 and 12, the deflection of the shafts 21and 22, such as it may be, renders them parallel. This correction fordeflection may be provided for in the mounting of the housing 14, aswell as in the mounting of the housing 13.

The feed shell 16 is adjusted by means of the worm 46 so that the slots49 thereof will pass through the plane Y when the opposing peripheriesof said die rolls are in phase. A means 30 for supplying the screwblanks 5%] to the slots 17 is then provided and the machine 10 is readyfor operation. It will be observed that the machine 10 in thisparticular embodiment slopes rearwardly and downwardly at an angle ofbetween approximately 10 and 15", as shown in Figure 2. The purpose ofthis is to utilize gravity in preventing the accidental discharge of thescrew blanks 50 from the front ends of said slots I17, particularlywhere the screw blanks are provided with eads.

In order to overcome the scoring of the trailing wall 53 of the slots 17by the screw threads 52 as the diameters of the blanks 50 expand duringthe rolling process, said screws are accelerated as they advance betweenthe die rolls 11 and 12 slightly faster than the movement of the slots17. This is accomplished as stated above, by increasing slightly thediameter of the faster moving of said die rolls, or by permitting anaxial shift of one of said die rolls with respect to the other. Ineither case, the phase is accelerated by an amount equal to one-half theincrease in the thickness of said screw blank as the thread 52 is rolledinto said blank.

If, as stated above, the differential in peripheral speeds isaccomplished by having different diameters for the die rolls 11 and 12,the acceleration in the advancement of the screw blanks 50 between thedie rolls 11 and 12 may be accomplished by substantially the samemethods. Whether the difference in peripheral speeds is accomplished bya difference in the diameters or by a difference in the rotationalspeeds of said die rolls, the number of starts b and the helical slopeof the helical grooves 51 remain the same in applying either method ofovercoming or avoiding injury to the screw threads 52 from scoring orjamming.

If it becomes desirable to change the pitch and/or diameter of the screwto be produced by'the' machine 10, new die rolls 11 and 12 must beprovided, and substantially the same adjustments must be made asdiscussed hereinabove in detail.

The relative position of the feed shell 16 with respect to the die roll12, which it encircles in this particular embodiment, may be adjustedcircumferentially by means of the adjustment head 48, either while themachine is standing idle or is in operation. However, when suchadjustment has been made, the fee'd shell 16 will then rotate, due toits geared connection with the die shaft 22, at a constant speed.Likewise,"said rolls 11 and 12 will also be rotated at constant speedsin order toavoid an unintentional and undesirableshift in the phaserelationship between the helical grooves on the two die rolls. Once thisphase relationship hasbeen established, it will remain constant untilchanged by manual operation of theworm gear 46 and the resultingnotation of the rear ring 44. v I v Although a particular, preferredejmbodiment of my in vention has been disclosed hereinabove forillustrative purposes, it will be' understood that variations andmodifications thereof which do not depart from the scope of suchdisclosure are fully contemplated unless specifically stated to thecontrary in the appended claims.

I claim:

1. A machine for cold rolling threads onto screw blanks, comprising: apairof radially aligned die rolls having substantiallyparallel axes andaplurality of adjacent and uniform helical grooves of identical pitchand slope disposed along their peripheries, the distance between saidperipheries being less than thediameter of said blanks, and therebydefining a zone of engagement between each blank and said peripheries,said blanks having a position of entry intos'aidzone parallel with saidaxes; drive means for. rotating said rolls simultaneously in the samerotational direction at different peripheral speeds, whereby a pluralityof similar phases in the relationship between said grooves will occuradjacent to said position of entry at uniform intervals and then move ata constant rate of speed through said zone transversely of said axes; acylindrical feed shell concentrically encircling one of said rolls andmoving through said zone,

said shell having a plurality of radially disposed,.parallel slotstherethrough, each slot being circumferentially wider than the diameterof said blank; driven means actuated by said drive means for positivelyrotating said shell at a peripheral speed substantially equal to halfthe difference between said peripheral speeds of said rolls, said slotsbeing moved between said rolls in the same direction as the fastermoving one of said peripheries and at approximately the same rate assaid phases, said blanks being moved into said position of entry by saidshell when and only when one of said similar phases in said groovesoccurs adjacent said position of entry; and said driven means includingmeans in the form of positively engaged elements for adjusting the driverelation between said shell and said one roll for adjusting the relativepositions of said slots and said phases Within said zone.

2. A machine according to claim 1 wherein said rolls are secured todrive shafts and including means for rotating said drive shafts at apredetermined speed ratio with respect to each other; and wherein saidpositively engaged elements include an external gear secured to thedrive shaft for said one roll, first and second ring gears coaxiallyencircling said external gear and having different pitches, said firstgear being secured to said shell and said second gear being held againstrotation with said shell, a plurality ofplanet gears engaged betweensaid external gear and said ring gears, whereby rotation of saidexternal gear efiects a rotation of said second gear with respect tosaid first gear.

3. A machine according to claim 2 wherein said first ring gear hasexternal teeth; and including a Worm meshing with the external teeth onsaid first ring gear and means for manually rotating said worm, wherebysaid shell is rotated with respect to said one roll to adjust therelative positions of said slots and said phase points within the zonedefined by the bite of said rolls.

References (Iited in the file of this patent UNITED STATES PATENTSGermany Nov. 15, 1954

